The present disclosure relates to a trench diode, a power semiconductor device including a trench diode, and a method for forming the trench diode.
Power semiconductor devices are used in many different industries. Some of these industries, such as telecommunications, computing, and charging systems, are rapidly developing. Those industries would benefit from improved semiconductor device characteristics, including reliability, switching speed, and miniaturization.
Power semiconductor devices use a Zener diode for electrostatic discharge (ESD) protection or clamping when performing inductive switching. A conventional Zener diode is a surface-formed Zener diode that is formed on a thick insulator over a trench gate of a MOSFET, i.e., after gate polysilicon has been formed in a trench. Therefore, the surface-formed Zener diode needs additional poly deposition and masking implantation after the trench MOSFET formation. In addition, since the conventional surface-formed Zener diode is formed over the trench MOSFETs, the conventional surface-formed Zener diode adds to surface topology, which makes it more difficult to pattern small features during lithography. The conventional surface-formed Zener diode, due to its added height, also triggers step coverage issues when multiple metal deposition processes are performed.